Nonflammable organic heat transfer agent



atente July 8, E41

NONFL 1: LE ORGANIC HEAT SFER AGENT Ray H. Boundy and Robert R. Dreisbach, Midland, Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Application April 29, 1939, Serial No. 270,903

3 Claims.

This invention concerns certain new non-flammable liquid organic heat transfer agents which contain as the essential ingredient a mixture of compounds having the formula It will be seen from the properties just given that each of these mixtures of isomeric dihalofiuorobenzene are adapted to use at atmospheric pressure as a heat transfer agent at temperatures 01 I 5 considerably below the freezing point and above the boiling .point of water. Accordingly, these g2 mixtures may be used as refrigerants at tempera- X tures far below 0 C. or as heat transfer agents. wherein X is chlorine or bmmine e. g. radiator fluids for internal combustion en- The dihalo-fiuorobenzenes having the above f at temPemtures rangnigup to from 172.0 to formula are prepared by chlorinating fluoroben- 194 Thelr -P w r zene to form dichloro-fluorobenzene or by succesness ,toward me ta'lsr and then of sively chlorinating and brominating the fluorophyslcal propert! render them Ideallysumed to benzene to obtain chloro-bromo-fluorobenzene, these and Var 3 of heat transfer depending upon which product is desired. After poses- By employmg them m a closed System at completing the halogenation, the produ is super-atmospheric pressure, they may, of course, treated, e. g. with an alkali, to remove any disbe used r t ns er purposes at temperasolved hydrogen halide and is distilled to separate consldembly above normal bollmg the dihalo-fluorobenzene product. In this dispomts at p t res of 350 to 409 C. or tillation, it is not essential that the dihalo-fluoroe In all Such heat transfer eperatlons, as benzene be completely ifi d since the retem is well known, the liquid heat transfer agents is tion f by..product such as trichlommuombem contacted simultaneously or alternately with a zene, dichloro-bromo-fluorobenzene, etc., which relatively ts the cylinder block of usually are formed in minor proporti along an internal combustion engine-and a relatively t t dihahdumbenzene, is t detrimenmL cool surface, e. g. themetal surfaces of a radiator, Unreacted fluorobenzene, and, any low boiling whereby heat iS caused to flOW f the ve y flammable by-products such as monocmomhot surface to the liquid heat transfer agent and fluorobenzene, are of course preferably removed from the letter to the relatively 6001 Surfacein the distillation, although the presence of up Although the above-described d o-fiuo to 10 per cent by weight of chloro-flu'orobenzene' benzene isomeric x e r each w suited does not render the product flammable a d may to use without dilution as a heat transfer agent, be tolerated in those instances where the low y are usually employedinadmixture W t Ot boiling point of this ingredient is not objectiona at d a m tic yd a such es able. ortho-dibromobenzene, trichlorobenzene, tetra- The dichloro-fluorobenzene d h1 -b chloro-benzene, dibromo-toluene, etc., which are fluorobenzene products prepared as just described either non-flammable or difiicultly fla e. are thin liquid mixtures of isomeric compounds. but Which, because f t i relatively high ee We have found that they possess an unusual ing temperatures r o h r Objectionable P p combination of properties which rend rs th m ties, are not as well suited to be used alone for especially useful as the essential ingredients in 40 u p p s s as are the diha e-fiuorobenzenes. a series of new liquid heat transfer compositions y d t he diha o-fluerobenzene mixtures which are suitable for use over a considerable with S Other o e a d a a hydrocarrange of temperatures. They are non-flammable ns, h st f th final pr du m be and are substantially non-corrosive toward the duced and the properties desired in the heat usual structural metals, such as iron, steel, alut a s r a ts. g. l w fr point r low minum, etc. They have low freezing points, high viscosity, etc., may often be improved. Such heat boiling temperatures, and viscosities sufliciently transfer agents comprising the dihalo-fluorolow to permit ready flow with excellent heat transbenzene isomers along with other halogenated fer under the usual working conditions. Their aromatic hydrocarbons are compounded so as to physical properties are asfollows: remain liquid at temperatures below -20 C.,

o Viscosityirt millipoises Isomeric mixture 21 2 760 5 b a o r. F. 235 F.

Dichlonrfluorobenzenesun 172 -35 1.407 30.2 10.4 4.75 Chloro-bromo-fluorobenzones 194 26 1. 7277 14. 4 6. 1

. and preferably below 25 0. They usually contain at least 20 per cent by weight, and preferably more than. 50 per cent, of the dihalofluorobenzene isomers.

The following examples describe several heat transfer compositions which have been prepared in accordance with the invention, but are not to be construed as limiting the invention.

Example 1 To 9 parts by weight of the isomeric mixture of dichloro-fluorobenzenes, prepared by the' Example 2 To 4 parts by weight ofthe isomeric dichlorofluorobenzene mixture mentioned in Example 1, there was-added 1 part of a mixture of isomeric chloro-bromo-fluorobenzenes, prepared by the successive chlorination and bromination of fluorobenzene. The resultant solution was a clear liquid at -29 C., but froze at temperatures between 30 and 34 C. It boiled at atmospheric pressure over the temperature range 174- 186 C. It had the specific gravity 1.526 at F. or 1.343 at 250 F., and the absolute viscosity 33.80 millipoises at 0 F., or 4.65 millipoises at 250 F. It was non-flammable and substantially non-corrosive toward usual structural metals, e. g; iron, steel, aluminum, 'etc.

. Ezvample 3 To 82 parts by weight of the dichloro-fluorobenzene isomeric mixture mentioned in the preceeding examples there were added 9 parts of ortho-dibromobenzene and 9 parts of trichlorobenzene. The resultant solution was a thin nonflammable liquid which remained clear and Example 4 A non-flammable thin liquid heat transfer agent was prepared by adding to 75 parts of dichloro-fluorobenzene, 17 parts of chloro-bromofluorobenzene and 8 parts of trichlorobenzene. The resultant solution was a clear liquid at -30 C., but froze at temperatures from -32 to 35 C. It boiled over the temperature range 172- 193 C.; had a specific gravity of 1.505 at 0 F. or 1.327 at 250 F.; and an absolute viscosity of 33.70 millipoises at 0 F. or 4.76 millipoises at 250 F.

Other modes of applying the principle of the invention may be employed instead of those explained, change being made as regards the compositions herein disclosed, provided the ingredient or ingredients stated in any of the following claims or the equivalent ofvsuch stated ingredient or ingredients be employed.

We therefore particularly point out and distinctly claim as our invention:

1. The method of transferring a heat which comprises contacting a non-flammable liquid, containing as an essential ingredient a mixture of compounds having the formula wherein X is.a halogen substituent of the class consisting of chlorine and bromine, with a relatively hot surface and with a relatively cool surface, whereby heat flows from the relatively hot surface to the liquid and from the latter to the cooler surface.

2. The method of transferring heat which comprises contacting a non-flammable liquid, having a freezing point below 20 C. and consisting essentially of a mixture of nuclearly halogenated aromatic hydrocarbons containing at least 20 per cent of isomeric dichloro-fluorobenzenes, with a relatively hot surface and a relatively cool surface, whereby heat flows from the relatively hot surface to the liquid and from the latter to the cooler surface.

3. The method of transferring heat which comprises contacting a non-flammable liquid, having a freezing point below -.-20 C. and containing at least 50 per cent of an isomeric mixture of dichloro-fluorobenzenes and a minor proportion of a nuclearly halogenated aromatic compound selected from the class consisting of chlorobromofiuorobenzene, ortho-dibromobenzene and trichlorobenzene, with a relatively hot surface and with a relatively cool surface, whereby heat flows from the relatively hot surface to the liquid and from the latter to the cooler surface.

RAY H. BOUNDY.

ROBERT R. DREISBACH. 

